A commonly accepted method of characterizing electrical networks is a measurement of so called scattering parameters, also known as S-parameters. S-parameters describe electrical waves that are reflected from or transmitted through the device under test (DUT).
While the method's success and usefulness is unprecedented and unquestionable, its implementation becomes increasingly more difficult as the frequency coverage of modern network analyzers increases and the test is performed in harsher and harsher environments. For example, in the case of measuring S-parameters at optical frequencies, the laser phase noise makes a direct measurement of phase very difficult if not impossible. In addition, the DUT itself may be a spool of fiber that is 100 km long and very sensitive to environmental changes, therefore corrupting the phase of even the most stable laser sources.
Thus it would be desirable to provide a more convenient and more reliable method and system to measure and characterize an electrical system or network.